The invention concerns a method and device for ventilating a room with ceiling and walls, whereby clean air is conducted to at least a portion of the room from the ceiling through a first air stream.
Rooms of this type for which the invention is especially suitable occur above all within the area of health care but also within certain industries in the form of so-called clean rooms. Clean rooms are used for the production of integrated circuits, among other purposes, where the prevention of the occurrence of dust particles in the proximity of certain surfaces of materials can be decisive. In the area of health care the concern is primarily with operating rooms and similar, in which the number of air-borne particular contaminants that may carry bacteria must be kept down.
Methods have been developed according to which air is conducted to smaller portions of the room through directed air streams. This, however, risks ancillary injection of insufficiently purified air.
A system that to a certain degree avoids problems of additional injected air is shown and described in the WO86/06460 system. The system comprises a horizontal ceiling unit from which clean air is conducted to a space, and a vertical wall unit from which air is conducted substantially horizontally. Between the ceiling unit and the wall unit additional air outlet devices are located in order to bring about a diagonally directed air supply downwards in the form of an air curtain. The air curtain decreases the risk that air with undesirable particles is carried along with the stream of clean air.
With the embodiment according to WO86/06460 turbulence can occur at the intersections between the room""s walls and ceiling. A certain risk thus remains that air passing over the floor of the room will pick up particles that are directed into the air stream along with clean air. Turbulence can, for example, lead to contact of the air stream with the floor and other dirty surfaces and then mix with an air stream with clean air.
Another prior art document is U.S. Pat. No. 4,693,175, which discloses a clean room system having fan filter units. A main supply air duct is connected to each fan filter unit through a branched supply duct to which a branched return duct is connected such as to introduce a part of the return air from the room in the main return duct. Thus, to each fan filter unit are introduced open air conditioned by an air conditioner and a part of the return air from the clean room.
One object of the present invention is to provide a method of circulation in a room, whereby the risk of contaminated air mixing with the clean air is further decreased. Another object is to provide a device designed for ventilation of a room that is embodied so that the risk that contaminated air mixing with the clean air is further decreased.
These objects are achieved in that the invention has received the special features cited in the independent patent claims.
According to the invention a portion of a room is supplied with air from above, preferably from the underside at the ceiling. Air exiting from the room is to a great extent exhausted through discharge openings at the level of the floor, but a portion thereof is exhausted along at least one of the walls of the room. The portion of the air that is not directly exhausted through the floor openings leaves the room through a discharge opening along the wall of the room.
In an embodiment according to the invention an air output device is located on the ceiling of the room. The air output device is designed with a substantially smooth underside and with diagonal side surfaces turned towards the walls. Both the underside and the side surfaces comprise perforated portions through which the clean air is conducted into the room.
Between the air output device and the sidewalls of the room, discharge openings are located at ceiling height through which air exiting the room is exhausted. In a preferred embodiment, the discharge openings are located along all the sidewalls of the room.
Between the air output device and the discharge openings, diagonally placed and curved flow directors are located that direct the clean air streaming out from the air output device downward. The flow directors to a great extent also prevent the out-flowing air from being directly exhausted through the discharge openings.
The term xe2x80x98clean airxe2x80x99 is understood here as air purified of particles as well as sterilized or disinfected air.